Add possibility to define average_length for monsters in JSON.

This change will allow to define length for monsters in JSON. It complements Kevins
fix for issue CleverRaven#40446. Along with that it also implements check for quartered corpse.

references CleverRaven#40446

This commit adds definition of "average_length" from JSON and adds it as
attribute longest_side of the monster type object. Referrence is then used
to define "length" in the item generation. Utilizing Kevins' addition
to default based on the items volume.

data/json/monsters/fish.json

@@ -225,6 +225,7 @@
     "id": "mon_fish_rainbow_trout",
     "type": "MONSTER",
     "copy-from": "mon_fish_medium",
+    "average_length" : "16 cm",
     "name": { "str": "rainbow trout" },
     "looks_like": "mon_fish_trout",
     "description": "A rainbow trout.  A fish made popular by father-son fishing trips, except for the part where you have to gut it."

src/item.cpp

@@ -4656,13 +4656,27 @@ units::mass item::weight( bool, bool integral ) const
     return ret;
 }
 
+// corpse longest side helper for  item::length
+units::length item::corpse_length( const mtype *corpse ) const
+{
+    units::length corpse_length = corpse->longest_side;
+    if( has_flag( flag_QUARTERED ) ) {
+        corpse_length /= 4;
+    }
+    if( corpse_length > 0_mm ) {
+        return corpse_length;
+    }
+    debugmsg( "invalid monster length for corpse sending default from volume" );
+    return units::default_length_from_volume<int>( corpse->volume );
+}
+
 units::length item::length() const
 {
     if( made_of( LIQUID ) || is_soft() ) {
         return 0_mm;
     }
     if( is_corpse() ) {
-        return units::default_length_from_volume<int>( corpse->volume );
+        return corpse_length( corpse );
     }
     return type->longest_side;
 }
@@ -4689,6 +4703,8 @@ units::volume item::corpse_volume( const mtype *corpse ) const
     return 0_ml;
 }
 
+
+
 units::volume item::base_volume() const
 {
     if( is_null() ) {

src/item.h

@@ -542,6 +542,10 @@ class item : public visitable<item>
         /** Volume check for corpses, helper for base_volume(). */
         units::volume corpse_volume( const mtype *corpse ) const;
 
+
+        /** Length check for corpses, helper for length(). */
+        units::length corpse_length( const mtype *corpse ) const;
+
         /** Required strength to be able to successfully lift the item unaided by equipment */
         int lift_strength() const;
 

src/item_factory.cpp

@@ -450,7 +450,7 @@ void Item_factory::finalize_pre( itype &obj )
     }
 
     if( obj.longest_side == -1_mm ) {
-        obj.longest_side = units::default_length_from_volume<int>( obj.volume );
+	obj.longest_side = units::default_length_from_volume<int>( obj.volume );
     }
 }
 

src/monster.cpp

@@ -2673,6 +2673,12 @@ units::volume monster::get_volume() const
     return units::operator*( type->volume, get_size() / type->size );
 }
 
+units::length monster::get_length() const
+{
+    return units::operator*( type->longest_side, get_size() / type->size );
+}
+
+
 void monster::add_msg_if_npc( const std::string &msg ) const
 {
     if( g->u.sees( *this ) ) {

src/monster.h

@@ -111,6 +111,7 @@ class monster : public Creature
         units::mass get_weight() const override;
         units::mass weight_capacity() const override;
         units::volume get_volume() const;
+        units::length get_length() const;
         int get_hp( hp_part ) const override;
         int get_hp() const override;
         int get_hp_max( hp_part ) const override;

src/monstergenerator.cpp

@@ -704,6 +704,7 @@ void mtype::load( const JsonObject &jo, const std::string &src )
     assign( jo, "bodytype", bodytype );
     assign( jo, "color", color );
     assign( jo, "volume", volume, strict, 0_ml );
+    assign( jo, "average_length", longest_side );
     assign( jo, "weight", weight, strict, 0_gram );
 
     optional( jo, was_loaded, "phase", phase, make_flag_reader( gen.phase_map, "phase id" ), SOLID );

src/mtype.h

@@ -246,6 +246,7 @@ struct mtype {
         nc_color color = c_white;
         m_size size;
         units::volume volume;
+        units::length longest_side = -1_mm;
         units::mass weight;
         phase_id phase;